Build Your Dream Boat #10
Posted by Gayle Brantuk on Jul 30th 2010
Just as promised in my last post, this is all about the building form of your boat. My father wrote the following article which really paints a vivid picture of what is involved in the process.
There are a couple of terms in the article that not everyone will understand so here are the definitions:
Athwartship(s) – Across the boat. Longitudinals – Hull framing members that run the length of the boat.
Enjoy the article…
Setting up – The foundation for building a boat By Glen Witt
A boat, unlike a house or garage, does not have flat areas such as a level foundation with vertical uprights (studs), etc. A boat is curved from most any direction you view it. An artificial foundation must be created. We’ve developed a method of using a “building form” to substitute for the “foundation” in the analogy with housing construction. This type of building form is used on conventional boatbuilding, wood, metal, or fiberglass but is not required for stitch-n-glue boatbuilding.
The conventionally built plywood boat is built around a series of sectional members called frames or bulkheads. We furnish full size patterns to make your own. Our system utilizes an athwartship horizontal reference line across each frame. On most small boats this is the inside surface of the bottom frame member. However, it may be a horizontal cross member at most any selected height on the frame. The frame centerline is perpendicular to this horizontal reference line that we call the “set up level”. The set up level is also parallel to the waterline thus forming a horizontal plane level both lengthwise and athwartship through the boat.
When the frames are aligned vertically and horizontally, the curved boat shape is automatically developed. These frames and other hull framework members are supported by the building form. This is simply a method of supporting the frames and other members such as stem and transom accurately at the set up level.
Several types of forms can be used but generally we prefer one developed over the years that has proven simple and accurate. The frames and other members are supported by two longitudinal members (set up members) that are level both lengthwise and athwartship, at a convenient working height, and spaced a width compatible with that of the frames. These longitudinal members are supported to the ground or working areas by upright legs.
inboard powered, the set up members double as motor stringers to support the weight and spread it through the structure. Set up members on smaller boats and those outboard powered are used only to build and are not a part of the finished boat.The longitudinal set up members may remain part of the boat. Often they are used as longitudinal supports for floors, cabinetry, etc. If the boat is
It is not necessary that the ground or floor is level; only that the set up members be level in both directions. Obviously you don’t want to work on the side of a hill but a level surface is not necessary. In days gone by, the typical beginning of construction started with building a level floor to build the boat on. Great idea but expensive and not required with the method we have developed.
The upright legs supporting the set up members may be posts buried in the ground if working on a dirt area. Some will have the advantage of building on a paved area, however, it’s doubtful if you want to bust it up and put in posts. To overcome this we use a horizontal base member anchored to the ground with expansion bolts. This base member is used with cross members to support the legs.
Most of our plans detail, dimension, and give instructions for a building form specifically for the boat being built and even list the sizes and materials required. But the building wood sizes or type is not critical and any scrap lumber can usually be substituted.
The frames and other parts that form the hull structure must be rigid. Longitudinals will be bent around this framework that will require shoving, pulling, etc.; the structure must not move or the hull shape may be distorted. Fasten the frames securely to the set up members. Upright blocks from the set up members fastened to the frames with screws, bolts, double-headed nails, or clamps will do the job. Or use an athwartship cleat atop the set up members and fastened to the frame or cleat on the frame set up level, fastened by any method listed above. Remember the fasteners will be removed to lift the boat from the building form. Don’t position fasteners in such a manner that they are inaccessible and cannot be removed easily.
Brace the framework with cross braces between frames or block the frames to the floor. Perhaps a ceiling or wall is available for anchoring the bracing to the framework. Usually some of the braces can be removed just before planking the hull. Better to have more bracing than not enough.
A well built building form, with accurate frame members properly centered, leveled, and securely held in place, will provide the sound foundation for the construction of the balance. Spend a little time to make it correctly and time spent fixing goofs will be virtually eliminated.
Here are some photos to show what the building form actually looks like… I really like the illustration my father used in the article comparing the building form to the foundation of a house. I think that really puts it into perspective.
Doesn’t look too difficult, does it? Most who build our boats are first time builders, so experience definitely isn’t required. Until next time… build more boats, Glen-L boats that is…